From 2e933b1274dc89cd1629f6c7fd9bf952248d84c2 Mon Sep 17 00:00:00 2001 From: Taeung Song Date: Mon, 27 Mar 2017 16:10:37 +0900 Subject: [PATCH] perf annotate: Fix a bug of division by zero when calculating percent Currently perf-annotate with --print-line can print -nan(0x8000000000000) because of division by zero when calculating percent. The division by zero happens when a sum of samples is zero in symbol__get_source_line(), so fix it. For example: After running 'perf record' like below, $ perf record -e "{cycles,page-faults,branch-misses}" ./a.out Before: $ perf annotate --stdio -l Sorted summary for file /home/taeung/workspace/a.out ---------------------------------------------- 32.89 -nan 7.04 a.c:38 25.14 -nan 0.00 a.c:34 16.26 -nan 56.34 a.c:31 15.88 -nan 1.41 a.c:37 5.67 -nan 0.00 a.c:39 1.13 -nan 35.21 a.c:26 0.95 -nan 0.00 a.c:44 0.57 -nan 0.00 a.c:32 Percent | Source code & Disassembly of a.out for cycles (529 samples) ----------------------------------------------------------------------------------------- : ... a.c:26 0.57 -nan 4.23 : 40081a: mov %edi,-0x24(%rbp) a.c:26 0.00 -nan 9.86 : 40081d: mov %rsi,-0x30(%rbp) ... However, if a sum of samples is zero (e.g. 'page-faults'), skip calculating percent. After: $ perf annotate --stdio -l Sorted summary for file /home/taeung/workspace/a.out ---------------------------------------------- 32.89 0.00 7.04 a.c:38 25.14 0.00 0.00 a.c:34 16.26 0.00 56.34 a.c:31 15.88 0.00 1.41 a.c:37 5.67 0.00 0.00 a.c:39 1.13 0.00 35.21 a.c:26 0.95 0.00 0.00 a.c:44 0.57 0.00 0.00 a.c:32 Percent | Source code & Disassembly of old for cycles (529 samples) ----------------------------------------------------------------------------------------- : ... a.c:26 0.57 0.00 4.23 : 40081a: mov %edi,-0x24(%rbp) a.c:26 0.00 0.00 9.86 : 40081d: mov %rsi,-0x30(%rbp) ... Signed-off-by: Taeung Song Tested-by: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Masami Hiramatsu Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Wang Nan Link: http://lkml.kernel.org/r/1490598638-13947-3-git-send-email-treeze.taeung@gmail.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/annotate.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c index 6dc9148..11af5f0 100644 --- a/tools/perf/util/annotate.c +++ b/tools/perf/util/annotate.c @@ -1671,11 +1671,15 @@ static int symbol__get_source_line(struct symbol *sym, struct map *map, src_line->nr_pcnt = nr_pcnt; for (k = 0; k < nr_pcnt; k++) { + double percent = 0.0; + h = annotation__histogram(notes, evidx + k); - src_line->samples[k].percent = 100.0 * h->addr[i] / h->sum; + if (h->sum) + percent = 100.0 * h->addr[i] / h->sum; - if (src_line->samples[k].percent > percent_max) - percent_max = src_line->samples[k].percent; + if (percent > percent_max) + percent_max = percent; + src_line->samples[k].percent = percent; } if (percent_max <= 0.5) -- 2.7.4